A ProMED-mail post
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International Society for Infectious Diseases
Date: 6 Jun 2010
Source: Bloodhorse.com [edited]
Two horses at Lone Star Park have tested positive for equine
piroplasmosis, a tick-borne disease caused by parasites that affects
horses, donkeys, mules, and zebras. In addition, a 3rd horse that
left Lone Star and had been shipped to New Mexico also tested
positive for the disease.
According to officials at the Texas track, one of the horses, Seven
Shooter, is trained by 2010 leading trainer Bret Calhoun, while
another, Street Positioning, is trained by Kevin Favre. Brian House
trains the horse that left for New Mexico.
As a result, horses in Calhoun's barn, as well as Favre's and House's
horses, have been restricted from racing and training with other
horses by the Texas Animal Health Commission, whose representative,
Bobby Crozier, is on the grounds at Lone Star.
"Right now, we are cooperating fully with the efforts of both the
Texas Animal Health Commission and the Texas Racing Commission," Lone
Star president and general manager Drew Shubeck said in a statement.
"We are following the direction (of Crozier), who has instructed us
to place restrictions on the horses of the affected trainers. We will
continue to work with the TAHC and Dr. Ken Quirk, the chief
veterinarian for the Texas Racing Commission, to resolve this issue
as quickly as possible."
"While we work toward resolution of the problem, we don't anticipate
any disruption in our racing schedule, which runs through 18 Jul
2010. We are also in discussions to make some adjustments in our
daily training schedule to allow the quarantined horses access to the
track for morning workouts."
Though equine piroplasmosis is primarily transmitted to horses by
ticks, the blood-borne disease has been spread mechanically from
animal to animal by contaminated needles. Once infected, an equine
can take 7 to 22 days to show signs of illness.
Cases of equine piroplasmosis can be mild or acute, depending on the
virulence of the parasite. Acutely affected equines can have fever,
anemia, jaundiced mucous membranes, swollen abdomens, and labored
breathing. Equine piroplasmosis can also cause roughened hair coats,
constipation, and colic.
In its milder form, equine piroplasmosis causes equines to appear
weak and show lack of appetite.
[Equine piroplasmosis results from infection by the protozoa _Babesia
caballi_ or _B. equi_ (phylum Apicomplexa). The 2 organisms may
infect an animal concurrently.
Equine piroplasmosis is a tick-borne protozoal infection of horses.
Piroplasmosis may be difficult to diagnose, as it can cause variable
and nonspecific clinical signs. The symptoms of this disease range
from acute fever, inappetence, and malaise, to anemia and jaundice,
sudden death, or chronic weight loss and poor exercise tolerance. The
disease may be fatal in up to 20 percent of previously unexposed
animals. The tick vectors exist in the United States, and epidemics
of piroplasmosis were seen in Florida in the 1960s.
The incubation period for _B. equi_ infections is 12 to 19 days, and
infections are more severe. For _B. caballi_ infections, it is 10 to
The clinical signs of piroplasmosis are variable and often
nonspecific. In rare peracute cases, animals may be found dead or
dying. More often, piroplasmosis presents as an acute infection, with
a fever, inappetence, malaise, labored breathing, congestion of the
mucus membranes, and small, dry feces. Anemia, jaundice,
hemoglobinuria, sweating, petechial hemorrhages on the conjunctiva, a
swollen abdomen, and posterior weakness or swaying may also be seen.
Subacute cases may have a fever (sometimes intermittent),
inappetence, malaise, weight loss, signs of mild colic, and mild
edema of the distal limbs. The mucus membranes can be pink, pale
pink, or yellow, and may have petechiae or ecchymoses. In chronic
cases, common symptoms include mild inappetence, poor exercise
tolerance, weight loss, transient fevers, and an enlarged spleen
(palpable on rectal examination). Foals infected in utero are usually
weak at birth, and rapidly develop anemia and severe jaundice.
In acute cases, the animal is usually emaciated, jaundiced, and
anemic. The liver is typically enlarged and dark orange-brown. The
spleen is enlarged, and the kidneys are pale and flabby. Petechial
hemorrhages may be seen in the kidneys, and subepicardial and
subendocardial hemorrhages in the heart. There may also be edema in
the lungs and signs of pneumonia.
The differential diagnosis for piroplasmosis includes surra, equine
infectious anemia, dourine, African horse sickness, purpura
hemorrhagica, and various plant and chemical toxicities.
Equine piroplasmosis can be diagnosed by identification of the
organisms in Giemsa stained blood or organ smears. _B. caballi_
merozoites are joined at their posterior ends, while _B. equi_
merozoites are often connected in a tetrad or "Maltese cross."
Organisms can often be found in acute infections, but may be very
difficult to find in carrier animals. In carriers, thick blood films
can sometimes be helpful.
Because _Babesia_ organisms can be difficult to detect in carriers,
serology is often the diagnostic method of choice. Serologic tests
include complement fixation, indirect fluorescent antibody (IFA), and
enzyme-linked immunosorbent assays (ELISA). The IFA test can
distinguish between _B. equi_ and _B. cabali_.
Other methods of diagnosis include DNA probes, in vitro culture, and
the inoculation of a susceptible (preferably splenectomized) animal
with blood from a suspected carrier. In addition, pathogen-free
vector ticks can be fed on a suspect animal, and _Babesia_ identified
either in the tick or after the tick has transmitted the infection to
a susceptible animal.
Disinfectants and sanitation are not generally effective against the
spread of tick-borne infections. However, preventing the transfer of
blood from one animal to another is vital.
The state of Texas and the state of New Mexico, in the South Central
to South Western United States, can be located on the
HealthMap/ProMED-mail interactive map at:
Equine piroplasmosis - USA (03): (TX, UT) 20100205.0395
Equine piroplasmosis - USA (02): (TX) 20100130.0322
Equine piroplasmosis - USA 20100129.0309
Equine piroplasmosis - USA (12): (NM) 20091230.4394
Equine piroplasmosis - USA (11): multi-state 20091203.4128
Equine piroplasmosis - USA (10) 20091117.3963
Equine piroplasmosis - USA (09): (NJ ex TX) 20091111.3912
Equine piroplasmosis - USA (08): (TX) alert 20091030.3749
Equine piroplasmosis - USA (07): (TX) 20091024.3675
Equine piroplasmosis - USA (06): (TX) OIE 20091022.3631
Equine piroplasmosis - USA (05): (TX) 20091021.3617
Equine piroplasmosis - USA (04): (KS, MO) resolved 20090917.3262
Equine piroplasmosis - USA (03): (KS, MO) 20090729.2662
Equine Piroplasmosis - USA (02): (MO) 20090612.2172
Equine Piroplasmosis - USA: (FL) quarantine lifted 20090225.0771
Equine Piroplasmosis - USA (04): (FL) 20080930.3088
Equine Piroplasmosis - USA: (03) (FL) 20080828.2687
Equine piroplasmosis - USA (02): (FL) 20080823.2626
Equine piroplasmosis - USA: (FL) 20080819.2579
Equine piroplasmosis - Georgia (USA) (2) 19960116.0097
Equine piroplasmosis - Georgia (USA) 19960112.0066]
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